What Lurks Within
by i am cloud
Summary: Tilly use to love Marais. That is, until she watched her brother drown. Now it only serves as a reminder of what she's lost. She thought that the town was part of a past she longs to forget. But when her grandma calls one night, begging her to come back, she can't find it in her to say no. The longer she stays in Marais, the more she learns that the swamp isn't ready to let her go.
1. Chapter 1

**Wow. Okay. DC really left us with a lot of unanswered questions, huh? Unless by some miracle the show is renewed, I'm going to pretend that I know what the show was going for. I might end this fic where S1 does, but I might also extend it a bit. I should know around the half-way point of this fic. **

**Disclaimer #1: Do I know anything about swamps? Not really. Please pretend that I know what I'm talking about. I did do as much research as I could, so hopefully I'm more accurate than I think I am. **

**Disclaimer #2: I do not own ****_Swamp Thing._**

**Trigger Warnings: Mentions of fat-shaming from a parent and the death of a child. **

* * *

Sunlight beamed down on the MacNulty twins as they raced through Marais' swamp. Their excited breaths echoed through the trees as their feet crunched the scattered debris. Come the beginning of June, this wasn't an uncommon sound. Summer break was what gave them the chance to explore the land beyond their grandma's back yard.

"Tristian, slow down!" called Tilly, her chubby legs struggling to keep up with her sibling's taller, skinner ones.

Her brother laughed in response as he threw her a cheeky grin over his shoulder. "Try to run faster, then!"

All Tilly could think of since they turned twelve was how Tristian seemed to be growing up quicker than her. He'd begun to lose his baby fat, his body starting to become lankier. Their dad kept saying how if he kept this up he'd become a basketball star once he reached high school. But whenever he looked at her, a girl who looked like she was nine rather than a pre-teen, it was with disappointment. She might be a kid, but she wasn't stupid. Tilly knew that he hated how she had the tendency to be more "piggish" than thin. (He had mentioned this during a few of their meals together.)

Tilly's usual outfits were over-sized and covered every inch of her skin. But that was more suited for a cooler environment. Louisiana summers were not very forgiving in regards to heat and sweat. Her grandmother had managed to somehow force her into a T-shirt and a pair of shorts. She'd protested at first, scared that Grandma Iris would sneer about how pudgy she looked. Tilly had shut-up when the threat of being kept indoors for the rest of the day was held over her head.

"You're too tall!" Tilly huffed, face red from the temperature and exhaustion. "I can't keep up!"

Tristian was about to say something snarky when the sound of a body hitting the ground forced him to skid to a halt. Tilly was on her hands and knees, tears dripping onto the mossy dirt. She trembled, shivering like a stubborn leaf, in an attempt not to scream in agony.

"Are you okay?" he asked, crouching before her.

"Ow," she moaned, teeth biting her lower lip.

"Where does it hurt?"

"Everywhere," Tilly sniffed. "I tripped over a root, and now my hands and knees hurt."

Without asking, Tristian grabbed his sister's left arm. Her scraped palm was coved in beads of blood and clumps of yuck. "You need Band-Aids," he remarked, gently tugging her back towards the direction of the house. It was at least a mile away, a trek that would take longer since they would be walking instead of sprinting. "Come on. Grandma will fix this."

Tilly only managed to give him a hiccup, reverting to their days as toddlers.

As they made their way back, Tristian told her fairytales to keep her mind off of her pain. The sound of thunder booming over head stopped him from telling her "The Frog Prince." The twins looked at a sky that had once been a cloudless blue as heavy raindrops dripped onto their dirty faces.

"I thought it wasn't gonna rain," said Tilly, brows brought down in confusion.

Tristian pulled, picking up their pace. "Guess they were wrong."

Like anyone who was familiar with the swamp, they knew that it was best to get out as quickly as possible. It wasn't safe to traverse it during bad storms, and the last thing you needed to do was to wait for it to clear. The ground would get mucky, sucking in feet and making it difficult to walk. Not to mention the gators that would soon begin to investigate the rising waters. They needed to get to their row boat before it became near impossible to see where they were heading.

With every hurried step the twins took, the heavier the rain became. Tilly had to squint her eyes and hold one of her forearms above them to get a semblance of her bearings.

"Tris, I can't see!"

"We've gotta keep going!"

"We need to stop!"

"No," he said, straining against the winds that had begun to pass through.

Tilly felt her heart pounding, the ache she'd acquired minutes ago pushed towards the back of her mind. "I'm scared," she admitted, voice too soft for her brother to hear over the sounds of the storm and swamp.

Soon enough, they reached their boat. It bobbed up and down where they had anchored it hours prior. Some of the rain had begun pooling in the center of it, adding even more urgency to the situation.

"Come on!" Tristian called over the rain.

Tilly crawled her way in, dreading the sting she'd feel once they began rowing away. She watched through her squinted gaze as Tristian joined her, pulling up their anchor. He let it plop on the boat, not caring to properly put it away.

"I got it," he told Tilly when he noticed her attempting to pick up her paddles. "Don't hurt your hands again."

And with that, they were off. The tiny tugs of the boat glided across the murky water, jerking them back-and-forth in their seats. They would be going much faster had she been assisting. The temptation to help, and the desperation to put an end to this unpleasant experience, gnawed at her. But every time she mustered up the courage to act on these feelings, she'd end up squeaking in discomfort.

"Stop it, dummy!" Tristian barked each time this happened.

It was during the fourth time she attempted to do this that she heard it. A boisterous _snap_ echoed around the twins. Something that was more deafening than the storm and the sound of water being struck by paddles. Like a giant crunching its foot on top of a thick log.

"What's that?!" Tilly exclaimed, pulse rushing as she turned herself to look at her surroundings. "Tris, what was that?!"

Tristian had ceased rowing, his eyes wide with dread and uncertainty as he scanned the area. "I -"

Tilly felt herself soar through the air, the boat she'd been in mere seconds ago flipping over with a noisy _splash_. The feeling of warm water embraced her, shadow black colors swirling before her. Tilly didn't know which way was up and which way was down. Had her instincts not kicked in, she would have swallowed something other than air. Panic had begun to set in when she felt a pair of hands grab and pull her.

Breaking the surface, Tilly gasped before a bout of coughing took its place. She wanted to scream, to let the fear welling up inside of her out.

Tristian shook her back to reality. "Swim, Tilly! Swim to land!"

He took off, body slicing its way towards the nearest muddy bank. If she managed to find enough strength, it wouldn't take her more than a minute to get to it. But she was so scared. Every part of her shivered as if she had been dropped into a vat of winter ice. Whatever had made their boat capsize was big and was set on hurting them. A heavy weight pressed around her, leading the poor girl to lose control of her common sense.

When he realized that his sister wasn't following him, Tristian stopped. He was so close. Only a few more mighty strokes and he'd be safe.

"Tilly! You gotta swim! You -"

Something pulled him back under, his arms shooting towards the sky as he let out a fearful gasp.

Tilly's line of sight remained focused on where her brother had been. Disbelieving. Worried. Afraid.

"Tris!" she screeched. "Tris!"

Branches groaned above her, drawing in her attention. They were moving like fat fingers, stretching downwards to where she treaded herself. A burst of adrenaline shot through her, making her turn around and try for the next closest strip of land. She needed to get out of the water, to drag herself away from its reach. Miraculously, she made it, pawing at the moss and soaked Earth - panting as tears fell down her damp face. She crawled, fingers digging in - breaking her nails and turning them into goops of scarlet. Tilly didn't stop until she found herself inches from a giant cypress. The exhaustion set in, every ounce of energy she might have had _whooshing_ out of her body.

As her eyelids began to droop, she couldn't bring herself to care about her surroundings. All she could do was fall into an immediate, heavy slumber as what was left of the rain thumped against her.

* * *

**I hope that you enjoyed reading this chapter. It's super important that we get a glimpse into Tilly's past. This traumatic experience is the beginning of an unpleasant childhood. We'll learn more about this in future chapters. **

**If the grammar sucks, I'm sorry. I was super excited to share this with everyone. I'll probably come back and edit this for the millionth time someday. That most-likely won't happen until November, though. **


	2. Chapter 2

**Disclaimer: I do not own ****_Swamp Thing._**

* * *

_Something lurked beneath the water, twisting and stretching its long body towards Tilly. She knew she should have run. That she should have screamed for help. Anything. But all she could do was remain frozen in the boat, widen gaze staring at what was unfolding before her. Heart thumping against her chest. Blood loudly pulsing through her. Ears roaring with panic._

_She didn't want to die. Not now, and especially not like this. To have her body rot deep within a swamp, skin oozing off of her bones as creatures feasted upon what was left of her. No one would be able to find her, and if they did, there wouldn't be much of her left at that point._

_Tilly let out a bloodcurdling scream when a hand roughly grabbed her arm, pulling her down into the depths below._

* * *

Tilly woke with a gasp, body jerking upwards as the feeling of being dragged downwards clung on to her limbs. Her breaths were heavy as she frantically searched for her lamp's switch. Relief began to surface as its yellow light blurred her vision, white spots dancing before her. She shifted her body until her legs hung over her bed, feet soon touching the room's plush carpet. Placing a hand over her chest, Tilly began to inhale and exhale, counting in her head as she began to ground herself.

_One. . . ._

_Breathe._

_Two. . . ._

_Breathe. . . ._

_Three. . . ._

_Breathe._

With each breath she took, the panic seeped away, the frantic beats of her heart calming down.

Another nightmare. Another moment back in the god forsaken swamp that had ruined her life.

She hissed, pushing the flood of memories to the back of her mind as they screamed at her to be remembered.

_Fuck off._

An anxiety attack was the last thing she was in the mood for, considering that she had. . . four hours before she needed to be up for work. The kids really didn't need to deal with a crabby teacher on the verge of tears. No. That was for her therapist.

A weight pressed itself onto her lap, drawing her attention to the one who had caused this. Billy, her beloved fat tabby, had curled himself on top of her. He softly purred, his little paws gently kneading themselves into her thighs.

Tilly smiled as she began to rub circles beneath his ear with the tip of thumb, his purrs becoming even louder.

"I can always count on you, bub."

Placing her hands under his tummy, she readied herself to put him back at the foot of the mattress. It was then that her cell lit up while the opening verse of "Iris" played throughout her room.

_Jesus. Who's calling me at two in the morning?_

Putting Billy down, Tilly sluggishly crawled over to her nightstand, more than ready to hit ignore. Worry ate away at her when she saw the name staring up at her and answered it as fast as her hands allowed her to.

"Grandma, what's wrong? Are you okay?" she got out in a rush as a long list of worse case scenarios raced through her mind. (She had fallen in the tub. She had lost the last of her arthritis pills. She had been stabbed by some maniac who had broken into her house.)

Nothing.

"Grandma?"

"_Tilly,_" her grandma shakily said. "_Oh, honey. It's so good to hear your voice._"

Her shoulders dropped, a weight leaving her chest as she realized that she wasn't hurt. . . . At least, she _thought_ she wasn't.

"Uh, you, too. What's going on?"

"_I -_"

A shocked gasp left the older woman, the sound of something clattering to the ground following the exclamation.

"Grandma?"

A few more beats passed, long enough for Tilly to think that the call had ended. She would have hung up, called again later on in the morning, but then she heard her grandma say, "_I need you, honey._"

"Need me?" Tilly asked, playing with a piece of the shirt she wore, biting the inside of her cheek. "For what?"

There were many things that Tilly would do for her grandma. She'd send her money if she was in a pinch. She'd call a mechanic for her if her car needed to be towed in for repairs. She'd even talk to her for hours on end if she wanted some company. But there was one thing in the world that she had told herself that she'd never do, no matter how much her grandma begged:

"_I need you to come back to Marais._"

Tilly felt like gaging when a lump rose to her throat while the memories she had barely suppressed minutes ago mercilessly hit her. Her head felt light as a rush of snapshots swirled around her mind.

_Tristian being pulled under the water._

_Waking up in the hospital a week later._

_Her dad looking at her with so much grief and hatred._

_Mom leaving them when she was fifteen._

_The shame she felt when she was left in rehab for the first time._

She folded into herself, teeth clenched together. Tears prickled at the corners of her eyes from the sting of being closed too tight.

_Anything but that. Please, god. Anything else._

"_. . . illy? Honey? Honey, please talk to me._"

"How could. . . how could you ask me that?" she managed to choke out.

"_Oh, Tilly. I'm so sorry._" Her grandma took a calming breath, mumbling something inaudible to. . . someone. . . before adding, "_I'll call your father._"

_Wait. What?_

"Why would you do that?"

"_Tilly, it's alright. I just need someone to come down here for a bit. He can -_"

Worry for her grandma's safety came back, nearly making her fall to the floor. There was no way in hell she could call that piece of shit. If what she needed help with was just the right amount of upsetting, he'd finally have an excuse to put her in a nursing home. From the horror stories she'd heard of neglect and lack of family visits other residents had experienced, that was the last thing she needed.

Not to mention the amount of guilt Tilly would feel knowing that she was the reason why her grandma withered away in a too-small room.

Fighting the protests in her head on what she was about to do, Tilly hesitatingly said, "How long do you need me for?"

* * *

Her boss wasn't thrilled when Tilly told her that she wouldn't be around for the last few weeks of school. Even though she hardly ever missed a day, that the reason she'd be gone was due to a family emergency.

That only added to the rising anxiety she felt, even after she took her medication to help suppress it. It helped knowing that they had a substitute who could look after her class for what little remained of the semester.

She felt horrible that she wouldn't be there for her class. That she wouldn't be able to say good-bye to them before they moved on to fifth grade. Tilly loved her job. She loved teaching those who would one day have an impact on everyone's future. That she was helping them grow into the people they were meant to be. That she was there to make sure that they had someone who believed in their abilities. Even if there were times where they tried her patience.

With how exhausted she was, driving wasn't the smartest thing to do. After getting things in order, she went back to sleep around three and didn't wake up until seven. It was enough to know that she wouldn't fall asleep while making the twelve-hour drive from Madison to Maris. With an army of coffee and whatever rock station she could find, she managed to drown out a majority of her thoughts. She only stopped for gas, the occasional bathroom break, and to give Billy the chance to do his thing.

Finally, after what had felt like an eternity, she saw the familiar sign for a town that had once brought her joy.

_Welcome to Marais!_

The letters screamed at her, making her heart pound louder and louder the closer she got. Her vision began to tunnel as her eardrums rang their warning. It was when her stomach sickeningly clenched that she swerved to the side of the road.

Tilly managed to park her car and open her door before a rush of caffeine and coffee cake tumbled onto the grass. She was able to cough up anything that had gotten stuck in the back of her throat before another round came around.

"_Fuck_," she weakly croaked, spitting out bile as grimy snot leaked from her nostrils.

Why did she think she could do this? If she couldn't handle a welcome sign, then how the fuck was she going to handle everything else?

"_This could be good for you,_" her therapist had told her while she drove through Illinois. "_Facing your fears head on. Letting yourself know that your past can't hurt you anymore._"

_Yeah fucking right._

A concerned meow came from Billy's carrier. He had pressed his pink nose against its netting as he attempted to set eyes on his owner. Tilly smiled, lightly placing a finger in front of Billy to let him know that she was feeling a little better.

"It's okay, bub. We're fine."

When she knew that Billy and her were on the same page, she rubbed her hands through her tangled hair. Perhaps this was a bad idea. Perhaps she should have let her dad handle this, as big of an ass as he was. Perhaps it would have been best if she had ignored that stupid phone call.

_Yep. I already regret this._

Then she remembered why she had pressed a forceful hand on her rising panic as she talked more with her grandma. If there was one thing she knew more than anything else, it was that her grandma deserved the best. For the kindness and love she had shown her since she was a kid. For how she'd opened her home to her and Tristian during their summer breaks. For how she had done her best to be there for her through the lowest points in her life.

What kind of person would she be if she turned on the greatest woman she knew in her time of need?

So Tilly kept her gaze focused on the road ahead as Joan Jett sang about how little she cared about her reputation.

And then, for the first time in thirteen years, Tilly crossed Marais' town line.

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**Thank you to everyone who has reviewed, favorited, and/or followed this fic.**

**I know this wasn't a super long chapter, but I do plan on the next one being a little longer. It's also when we get to see Tilly meet a certain biologist ;)**

**Until next time, see you later :)**


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